1. Field of the Invention
The present invention relates generally to a lock-type torque converter. Particularly, the invention relates to a lock-up type torque converter for an automotive transmission.
2 Description of the Prior Art
Conventionally, a lock-up torque converter for use in automotive transmissions, etc., are well known. For example, Japanese Utility Model Application, first publication (unexamined) 63-37859 discloses a typical example of such a conventional lock-up type torque converter. According to the above-mentioned Japanese Utility Model application, in order to ensure durability of a facing of a lock-up clutch which is frequently subjected to heat generated during lock-up and slip lock-up operations, a fixed orifice is provided at a circumferential portion of the facing in order to allow flow of automatic transmission fluid (ATF), to contact the facing for cooling thereof.
However, since the fluid flows from the time of engine starting, the fluid takes longer to reach an optimal running temperature. In conventional lock-up type torque converters, the temperature rises to an optimal running temperature fairly slowly and, for this reason, slip lock-up control cannot be effectively implemented immediately after engine starting. If slip lock control is effected before the temperature is sufficiently high, shuddering of the lock-up clutch may occur causing a loss of vehicle traction.
SAE paper No. 900810 discusses the relationship between temperature and shudder in automatic transmissions. According to the SAE paper, severe shudder was found at starting temperatures while no shudder is evident at running temperatures.
Therefore, it has been required to provide a lock-up clutch in which ATF temperature may rise quickly for reducing a period of time in which shuddering may occur after engine starting while maintaining the cooling characteristics of conventional fixed orifice type arrangements.